Magnetic sensors mounted at a magnetic reproducing head of a magnetic recording/reproducing device such as a hard disk drive include a sensor based on a magnetoresistance effect such as a giant magnetoresistance (GMR) effect or a tunnel magnetoresistance (TMR) effect. A magnetoresistive element used for these magnetic sensors is configured to include a ferromagnetic fixed layer having a fixed magnetization direction and a ferromagnetic free layer having a magnetization direction changing with external magnetic field, and a non-magnetic layer sandwiched therebetween, and operates based on a phenomenon where magnetic resistance of the element changes with the angle between the magnetization of the ferromagnetic fixed layer and the magnetization of the ferromagnetic free layer. In the case of magnetoresistive elements based on TMR, sense current flows in the film thickness direction. In the case of magnetoresistive elements based on GMR, they include a type of sense current flowing in the in-plane direction of the film and a type of sense current flowing in the film thickness direction.
Patent Document 1 describes a GMR element including a magnetic layer made of a half metallic material or a highly polarized material, thereby increasing the output of the GMR element, or a GMR element disposed on a 100% polarized spin injection layer and a barrier layer formed on a substrate, thereby increasing the output of the GMR element.